Apparatus for the manufacture of crimped bulky filaments

ABSTRACT

Improved apparatus by which a variety of crimped bulky filaments of uniform quality having desired crimp characteristics can be prepared with great operational advantages regardless of variations of the amount of the shrinkage of the filaments that cannot be avoided during the operation, by making it possible to fix in a stationary manner the point of separating crimped filaments from the screen at a desired and optional point without necessitating any performance of operational controls which are practically difficult or impossible, and various disadvantages in respect of the quality of the product and of the process operation that are inevitable in the known process because of the variations of the amount of the shrinkage of the filaments can be overcome.

United States Patent 11 1 Hino et al.

[ Nov. 20, 1973 APPARATUS FOR THE MANUFACTURE OF CRIMPED BULKY FILAMENTSInventors: Hazime Hino, Osaka; Magoichi I Saki, Itami; YoshihikoMaezawa,

Kyoto; Tsutomu Nakamura, Minohara; Nobuo Takahashi,both of Osaka, all ofJapan [73] Assignee: Teijin Limited,Osaka,Japan [22] Filed: Mar. 23,1971 [21] Appl. No.: 127,330

Related US. Application Data [62] Division of Ser. No. 5,224, Jan. 23,1970, abandoned.

52 US. (:1. 425/223, 28/1.4, 57/157 F, 425/224 51 1m. (:1. D02g 1/16[58] Field 1 Search 425/84, 223, 224; 28/1.6, 1.4, 72.12; 57/157 F [56]References Cited UNITED STATES PATENTS 3,143,784 8/1964 Scott 29/l.4 X

Primary ExaminerRobert L. Spicer, Jr. AttorneySherman and Shalloway [5 7ABSTRACT Improved apparatus by which a variety of crimped bulkyfilaments of uniform quality having desired crimp characteristics can beprepared with great operational advantages regardless of variations ofthe amount of the shrinkage of the filaments that cannot be avoidedduring the operation, by making it possible to fix in a stationarymanner the point of separating crimped filaments from the screen at adesired and optional point without necessitating any performance ofoperational controls which are practically difficult or impossible, andvarious disadvantages in respect of the quality of the product and ofthe process operation that are inevitable in the known process becauseof the variations of the amount of the shrinkage of the filaments can beovercome.

12 Claims, 18 Drawing Figures PATENTEUNUV 20 I973 SHEET 2 OF 3 APPARATUSFOR THE MANUFACTURE OF CRIMPED BULKY FILAMENTS RELATED U.S. APPLICATIONThis application is a division of U.S. Pat. application Ser. No. 5,224,filed Jan. 23,- 1970, now abandoned.

This invention relates to apparatus for improving a known process forpreparing crimped bulky filaments by impinging thermoplastic syntheticcontinuous filaments in a heated jet stream upon a moving screen havingnumerous perforations, passing the stream through the screen whileleaving the filaments on the screen to thereby form crimps in thefilaments and separating from the screen the crimped filaments whichhave been cooled according to the movement of the screen, whichapparatus can provide excellent crimped bulky filaments of uniformquality having desired crimp properties with great operationaladvantages regardless of variations of the amount of the shrinkage ofthe filaments that cannot be avoided during the operation, wherein thepoint of separating the crimped filaments can be fixed in a stationarymanner at a desired and optional point, whereby various disadvantages inrespect of the quality of the product and of the process operation thatare inevitable in the above known process because of the variations ofthe amount of the shrinkage of the filaments can be overcome withoutnecessitating any performance of controlling the feed rate of thefilaments, the velocity of impinging the filaments in a heated jetstream upon a moving screen and the velocity of separating andcollecting the crimped filaments from the screen according to thevariations of the amount of the shrinkage of the filaments, suchcontrols being, from a practical standpoint, difficult or impossible.

More specifically, this invention relates to an improvernent of theabove known process, characterized in that at the point where thecrimped filaments are separated from the screen means is provided topush the filaments on the screen to thereby fix the separating point ina stationary manner.

There has been known a process for the preparation of crimped bulkyfilaments which comprises projecting thermoplastic synthetic continuousfilaments such as continuous filaments of polyamides and of polyestersfrom a nozzle together with a heated stream of compressible fluid,impinging the projected thermoplastic "synthetic continuous filaments ina heated jet stream upon a moving foraminous surface such as a rotatingscreen disk or a screened endless belt, passing the stream through theforaminous surface while leaving thereon the continuous filamentsplasticized by the heated fluid, which is generally heated air or otherheated gas, forming crimps in the filaments by the impingement of thefilaments in a plasticized condition upon the foraminous surface, andtaking up from the foraminous surface the crimped filaments which havebeen cooled according to the movement of the surface (see U.S. Pat. No.3,156,028 and Canadian Pat. No. 636,056).

It is "easily understood that in the preparation of crimped bulkyfilaments of this type, unless the force retaining on the screen crimpedbulky filaments formed 'byimpingement of thermoplastic syntheticcontinuous filaments in a heated 'jet stream and in a plasticizedconditionis kept substantially constant,-'even when the separation ofthe filaments from the screen is-effected roll side. The force retainingthe filaments on the,

screen is influenced by various factors such as the configuration andperforation ratio of the screen, the kind of the filaments, the numberand denier of the monofilaments, the total denier of the filaments, therate of feeding the filaments to the jet, the temperature of the jetstream, the rate at which the filaments in a heated jet stream impingeagainst the screen, and the moving velocity of the screen. If thesefactors be kept substantially constant, it would be possible to keepconstant the filament-retaining force, with the result that the point atwhich the filaments are separated from the surface of the screen wouldnot vary if the take-up of the filaments is effected at a constant rateand under a constant tension.

However, in practical operation, even if the operation is carried outwhile controlling the above factors so as to prevent the change of theseparating point, it is impossible to substantially avoid the change ofthe separating point, though the change differs in degree to some extentaccording to circumstances, and it is impossible to foresee occurrenceof the change at all. This unavoidable and unforeseeable change of thefilamentseparating point is a great cause for variations in the qualityof the product. Indeed, it would be easy to say that such change couldbe overcome by conducting the continuous operation while changing thetake-up tension according to the change in the force of retaining thefilaments on screen. However, in the actual operation it is extremelydifficult to provide such control, because it is impossible to foreseeoccurrence of such change in the filament-retaining force.

As a result of various research made with a view to solving the abovetechnical problem, we have found that even when the abovementionedvarious factors are conditions, and even when these factors are madeconstant during the preparation of starting filaments, the variation ofthe amount of the shrinkage is observed among monofilarnents.Particularly in the filaments wound up onto a bobbin after the drawing,the amount of the shrinkage is apparently different between filaments inan inner layer of the pim and those in an outer layer of the pim. Thedifference of the temperature between the upper and lower limits of theprescribed temperature range gives a considerable variation to theamount of the shrinkage. Although it is highly desirable to:avoid suchvariation of the amount of the shrinkable in the filaments-as much aspossible, various technical and economical limitations are imposed onattainment of such trial in the actual operation. And, we have finallyfound that it is quite unreasonable to try to provide starting filamentsin which the change or variation of the amount of the shrinkage might bereduced to a negligible extent, in the preparation of crimped bulkyfilaments of the type intended in this invention.

Accordingly, we have furthered our research with a view to overcomingvarious disadvantages in respect of the quality of the product and ofthe process operation by fixing the above-mentioned point of separatingthe filaments from the screen by other means which may be industriallyapplicable, and to our great surprise it has been discovered thatcrimped bulky filaments of a uniform quality having desired crimpcharacteristics can be obtained regardless of the unforeseeablevariation of the amount of the shrinkage in filaments by utilizingextremely simple means that have neither been conventionally adopted inthe preparation of crimped bulky filaments of this type nor suggested toresult in great industrial advantages.

Further, a high speed processing operation is made possible by adoptingsaid means. In the conventional process and apparatus, in case thetake-up rate reaches, for instance, 500 m/min or more, since the take-uppoint comes nearer the projecting point of the nozzle, the time forfixing crimps becomes insufficient, with the result that the operationbecomes substantially impossible. In contrast, in accordance with theprocess and apparatus of this invention, such high speed operation ismade possible and the separation of the filaments can be effected at adesired and optional point stationarily.

Still further, in the conventional process and apparatus, in casefilaments are fed at a constant rate and taken up at a constant rate,the variation of the amount of the shrinkage in the filaments resultsinevitably in the shift of the point at which the filaments arerecovered from the screen and hence in the change of the distance alongwhich the filaments are cooled (the cooling time). Accordingly, in theconventional process and apparatus it is necessary to excessivelyprolong the distance for cooling in expectation of occurrence of suchchange or variation. It has been also found, however, that suchdisadvantage can be overcome by adopting said simple means in accordancewith the apparatus of this invention.

Still in addition, it has been found that in accordance with thisinvention it is possible to overcome another disadvantage of theconventional process and apparatus that since the shift of theseparating point changes the time required for cooling and solidifyingthe filaments crimped by impingement on the screen, if the operation iseffected while maintaining the stretching tension at a constant level atthe take-up point, the filaments are stretched under differenttemperature conditions and hence, unevenness of the percentage crimp iscaused to appear along the filament length.

Still further, in accordance with the apparatus of this invention, sincethe point at which the filaments are separated from the screen surfacecan be made stationary at a desired and optional point, it is possibleto vary the stretching tension at the take-up point within a broad rangeand hence provide crimped filaments rich in variety with improveduniformity and operability at low costs, which the conventional processand apparatus fail to provide.

Accordingly, a primary object of this invention is to provide improvedapparatus by which a variety of crimped bulky filaments of uniformquality having desired crimp characteristics can be prepared with greatoperational advantages regardless of variations of the amount of theshrinkage of the filaments that cannot be avoided during the operation,by making it possible to fix in a stationary manner the point ofseparating crimped filaments from the screen at a desired and optionalpoint without necessitating any performance of operational controlswhich are difficult or impossible from a practical standpoint, andvarious disadvantages in respect of the quality of the product and ofthe process operation that are inevitable in the known process becauseof the variations of the amount of the shrinkage of the filaments can beovercome.

Another objects and advantages of this invention will be apparent fromthe description given hereinbelow.

The above object of this invention can be achieved by the feature thatin conducting the above known process, at the point where the crimpedfilaments are separated from the screen an action of pushing thefilaments on the screen is given to the filaments to thereby fix thesaid separating point in a stationary manner.

For better illustration, the process and apparatus of this inventionwill be now detailed by referring to the accompanying drawings wherein;

FIG. l-A is a broken perspective of apparatus for preparing crimpedbulky filaments utilizing a rotary screen disc;

FIG. 1-8 is a broken perspective of apparatus for preparing crimpedbulky filaments utilizing an endless screen belt;

FIG. l-C is a broken side elevation of apparatus for preparing crimpedbulky filaments utilizing a suction device for maintaining the filamentseparation point stationary;

FIG. 2 is a top plan view of the rotary disc and conical pressing rollapparatus of FIG. l-A;

FIG. 3-A is a side elevation in section of a nozzle for use with theapparatus of the present invention;

FIG. 3-8 is a side elevation in section of a conventional nozzleproducing turbulent flow;

FIG. 4-A is a diagrammatic illustration of the assembly screen of thepresent invention;

FIG. 4-8 is a diagrammatic illustration of the operation of conventionalscreens;

FIGS. S-A and S-B are top plan views of assembly screens for use withthe present invention;

FIG. 6-A is a side elevation in section of an assembly screen disc foruse with the apparatus of FIG. l-A;

FIGS. 6-B and 6-B' are elevations of support structure for an assemblyscreen in accordance with the apparatus of FIG. l-B;

FIGS. 7-A, 7-B and 7-C are broken side elevations in section of nozzlesfor use with the apparatus of the present invention;

FIG. 8-A is a side elevation of an additional nozzle for use with theapparatus of FIG. 1-8; and

FIG. 8-B is a bottom plan view of the projecting outlet of theadditional nozzle of FIG. 8-A.

There has been well known an operation of preparing crimped bulkyfilaments which comprises impinging thermoplastic synthetic continuousfilaments in a heated jet stream upon a moving screen such as a rotaryscreen disk, an endless screen belt or a screen drum, passing the streamthrough the screen perforations while leaving the filaments on thescreen to thereby form crimps in the filaments, and separating from thescreen the crimped filaments which have been cooled according to themovement of the screen.

As the typical example of the above known operation, embodiments using arotary screen disk and an endless screen belt are illustrated in FIGS.l-A and l-B. In these embodiments, at the separating point an action ofpushingcrimped filaments on the screen is given to the filaments bymeans of a pressing roll 1 in accordance with this invention, and theseparating point is fixed.

In FIG. l-A, filaments f are fed at a constant rate to a jet 6 via, forinstance, a guide 5 by means of feed rolls 3,4. The filaments areaccompanied by a heated jet stream projected from the jet 6 and areimpinged upon a screen disk 7. The stream passes through the screen,while the filaments, which have been impinged on the screen in aplasticized condition, are left on the screen. Thus, crimps are formedin the filaments. According to the rotation of the disk (the rotationdirection is indicated by an arrow in the Figure), the filaments arecooled and the separating point is fixed at a suitable point on thescreen by means of the pressing roll 1. The filaments are taken up fromthe screen surface at the fixed separating point via, for instance, aguide 5 by means of delivery rolls. (not shown) similar to feed rolls3,4.

In case a screen of the type shown in FIG. l-A is used, it is importantto use a pressing roll 1 of a conical configuration, a plan view ofwhich is shown in FIG. 2, because a smooth rotation cannot be attainedby a pressing roll of a cylindrical configuration. In the case of ascreen of the above type, the filaments move on a locus of the circle ofa radius indicated as rf in FIG. 2 according to the rotation of thescreen while they are being cooled. In order for the conical pressingroll to rotate smoothly at the prescribed, filament-separating pointaccording to the rotation of the screen, it is essential that amongmaximum diameter D and minimum diameter D of the pressing roll, anddistance r, from the center of the screen to the point of said maximumdiameter and distance r, from the center of the screen to the point ofsaid minimum diameter, there be established a relation meeting theequation of D /R, D /r Thus, the screen and pressing roll can be rotatedwith- ;out causing any slip.

The pressing roll may be positively driven and rotated, or a free rollmay be adopted as the pressing roll. .In short, any means can be adoptedin this invention, as "far as they may impart an action of pushingfilaments on the screen (not by an excessive force but preferably,

'a force as mild as possible) to the filaments at the separating point.For instance, an apron roll, a pressing rod (snubbing rod an air suctionpump 23 disposed on the .side of the screen opposite the take-up roll,as shown ,in FIG. l-C and the like may be used in addition to-the jabovementioned pressing roll. In the case of an air suction pump, an actionof pushing the filaments on the .screen can be imparted by causing aforce of sucking the filaments on the screen downwardly via the screen.

FIG. l-B illustrates a similar embodiment where the operation isconducted in the same manner as above iexcept'that a screen of anend-less belt type is used in- ,stead of the above screen disk (feedrolls are not shown). The screen 7 spread onto rolls 8,8 rotated by[suitable means is moved by the rotation of the rolls 8,8

(the rotation direction is indicated by an arrow in the Figure), andfilaments are fed and impinged upon the screen to be crimped in themanner as above. Then, they are cooled according to the movement of thescreen and taken up from the screen at the prescribed separating pointfixed by a pressing roll 1 in the same manner as in the embodiment shownin FIG. l-A.

.In the embodiment illustrated in FIG. I-C, a suction device 23 isdisposed beneath screen 7 at the separa tion point for the filaments f,the suction device receiving air under pressure at an inlet port 24 andexpelling the air at an outlet port 25 to create suction at a suctionport 26. The suction port 26 is disposed on the side of the screen 7opposite the take-up roll 27 for the filaments in order to hold thefilaments against the screen at the separation point.

In this invention, the position at which the separating point is madestationary can be freely changed by changing the position at which meansfor imparting the pushing action to the filaments are placed, wherebyvarious modifications may be optionally devised. In addition, theconfiguration of crimps once formed in the filaments on the screen maybe also changed by varying the pushing action, the force of driving thepressing roll, the take-up rate, the take-up tension, etc., with theresult that it is possible to obtain filaments whose crimpcharacteristics are variant in a broad range.

In short, in this invention, since the point at which the crimpedfilaments are separated from the screen can be made stationary, the timeduring which the filaments are cooled according to the movement of thescreen can be also made constant, and a suitable take-up tension may befreely selected. Therefore, it is possible to obtain a product ofuniform quality at a high speed operation. It becomes also possible toattain high productivity by projecting filaments on one screen from aplurality of jets.

As described above, the take-up tension may be changed optionally inthis invention. However, in case the take-up tension is very high, thereis a tendency that while crimps are made latent under the tension, someof monofilaments constituting continuous filaments slacken and rise atsome points of the filament bundle along the length thereof.Accordingly, when it is intended to apply the product in an untwistedcondition directly to a knitting, weaving or tufting operation, suchslack in the monofilaments are likely to cause such operational troublesas yarn breakages and entanglements. In such case it is preferable thatthe take-up tension is adjusted to below 0.1 g/d when the crimpedfilaments are separated and taken up from the screen surface. Bycontrolling the take-up tension as above, it is possible to preventoccurrence of slack in the monofilaments, and a product which may beapplied directly in an untwisted condition to a knitting, weaving ortufting operation can be obtained advantageously. The above upper limitof the take-up tension may be preferably determined depending on thedenier of the filaments. For instance, in the case of filaments of ahigh denier such as in filaments for carpets, it is recommendable toadjust the take-up tension to below 0.05 g/d.

In this invention it is preferable to use a jet of a type capable ofprojecting a heated and compressed gaseous fluid accompanyingthermoplastic synthetic continuous filaments in a laminar flow withoutforming a turbulent flow and of impinging the filaments in the heatedjet stream against the screen in the state of parallel bundles. The useof a jet of such preferred type prevents the filaments impinged againstthe screen from scattering at random, and is effective for not onlyimparting uniform crimps to the filaments but also improviing thepercentage crimp, which will be defined below, while increasing theimpinging effect. Further, the use of a jet of such type is helpful toreduce the variation in the force of retaining the filaments on thescreen.

FIG. 3-A illustrates the section of a typical example of the jet meetingthe above requirements, and FIG. 3-B illustrates the section of anexample of a conventional jet which forms a turbulent flow therein.

The jet illustrated in FIG. 3-A comprises a housing 13 including a space2 in which a heated and compressed gaseous fluid is filled, and apassage 2 connected with said space 2 for projecting the fluid; an inlet14 provided for feeding the fluid to said space 2 in the housing 13; anda guide needle is for the filaments provided coaxially with said passage2' to penetrate said housing 13, said guide needle 15 running throughsaid space 2 and extending in the passage 2 at a length of less thanone-half of the whole length of said passage 2 to form an annularpassage 2" for the fluid between said needle 15 and the inner wall ofsaid passage 2'.

In FIG. 3-A, filaments which have been fed through a filament passageprovided in the guide needle 15 from a filament inlet 15' are projectedfrom the nozzle end in a plasticized condition together with a heatedjet stream which has been passed through the annular fluid passage 2"and the projection passage 2'. With the use of a jet of the abovestructure, it is made possible to impinge a heated jet streamaccompanying thermoplastic synthetic continuous filaments on the screenin the laminar flow state without forming a turbulent flow that isgenerally caused when a conventional crimping nozzle is used.

In FIG. 3-A the guide needle 15 is composed of one member, but it can beeasily understood that the guide needle may be composed of two memberscorresponding to the thinner tubular portion and the block-like upperportion in the Figure, respectively. The connection of the guide needle15 and housing 13 may be effected by insertion, hinging or any othermeans capable of combining them in a substantially air-tight manner.

The end point of the guide needle 15 extends into the projection passage2' and reaches the intermediate point of the passage 2' while formingthe annular passage 2". This feature promotes an action of separatingand opening individual nionofilaments constituting the continuousfilaments and directing them to the screen without causing a turbulentflow, namely without forming any substantial disorders or entanglements.The extending length of the guide needle 15 (indicated as AL in theFigure) is shorter than one-half of the whole length of the projectionpassage 2. In case the length AL is longer than the above limit, thoughthe effect of directing the filaments to the screen is heightened, it islikely that an action of sucking cool open air from the filament inlet15' to the filament passage in the guide needle is too strong. Inconstrast, in case this extending portion is not provided, a backwardflow of the heated and compressed gaseous fluid into the filamentpassage of the guide needle is likely to be too conspicuous. In short,it is preferable to adjust the length of the extending portion of theguide needle so that a light backward flow of the gaseous fluid may beallowed to occur. In

general, the length AL of the extending portion is shorter than one-halfof the whole length of the passage 2' (inclusive of the length of thepassage 2"), preferably shorter than 1.5 mm.

The introduction of the outer air into a nozzle by suction generallyresults in weakening the effect of heightening the temperature offilaments and bringing about other causes for unevenness in thefilaments. Such temperature or heating unevenness results finally in thedyeing unevenness. Accordingly, it is preferable to conduct theoperation in a manner such that a little backward flow may be allowed tooccur. This backward flow may be not only utilized for pre-heating thefilaments but also helpful to reducing the temperature or heatingunevenness to thereby attain a uniform dyeability in the productfilaments.

FIG. 3-B illustrates an example of the conventional nozzle (forinstance, a taslan nozzle) that causes inevitably a turbulent flow. Incase such nozzle is used as a jet, filaments introduced from thefilament inlet 15 un dergo a violent turbulent action under theinfluence of the fluid introduced from the fluid inlet 14, and they areconvoluted to scatter randomly at the impingement on the screen surface,with the result that the impinging effect is much lowered, thepercentage crimp of the product yarn is bad and a uniform processingeffect cannot be expected.

In this invention, it is possible and preferable to use an assemblyscreen previously proposed by some of the co-inventors of this inventionUS. application Ser. No. 847,548 filed on Aug. 5, I969 while effectingthe fixation of the separating point according to this invention.

More specifically, it is recommendable to impinge the filaments in aheated jet stream on an assembly screen comprising at least two adjacentlayers of screens and passing said stream through portions ofperforations of the lower screen overlapping each perforation of theuppermost screen under a resistance greater than that given when thestream has passed through the uppermost screen.

Although this type of an assembly screen is explained in detail in theabove mentioned patent application, a brief description will be nowgiven thereto in this specification.

The above assembly screen can cause an action like that of a stuffingcrimper in the screen depth through which the fluid passes, and canimpart to the filaments crimps of a high percentage crimp, say, about 40percent, which value could never be obtained by the conventionalprocess, without substantial increase of a disadvantageous reflection ofthe jet stream from the uppermost screen.

The above type of an assembly screen comprises at least two adjacentlayers of screens wherein a plane perforation area of each portion ofthe lower screen overlapping each perforation of the uppermost screen issmaller than the plane area of each perforation of the uppermost screenand said portion of the lower screen overlapping each perforation of theuppermost screen has an open space sufficient for the jet stream to passthrough said portion and freely escape from the assembly screen. It ispreferable that the spacing or degree of adjacency of the screen layersis in the range of from the state where the screen layers are in contactwith each other to the state where a distance of about 2 mm is formedbetween the screen layers, and that the perforation ratio of theassembly screen is in the range of from 30 to 70 percent.

FIG. 4-A is a diagram illustrating the principle of the operationaleffect attained by the use of such assembly screenfFIG. 4-B is a similardiagram illustrating the principle of the conventional process. FIGS.S-A' and S-B illustrate diagrammatically planes of two embodiments ofthe assembly screen. Other modifications are explained in detail in theabove-mentioned prior application Ser. No. 847,548.

A section of an assembly screen comprising two adjacent layers ofscreens is shown in FIG. 4-A. A portion of the upper screen composed ofmetallic wires 16,16 l6, and a portion of the lower screen composed ofmetallic wires 17,17 17 are shown in the Figure. Jet stream projected inthe direction indicated by arrows in the Figure impinges against thescreen and passes through it while leaving filaments in a plasticizedcondition in the assembly screen. In this case, the jet stream which haspassed through, for instance, the perforation between two neighbouringwires 16,16 of the upper screen, is obstructed by wire 17 of the lowerscreen at a portion of the lower screen overlapping the perforationbetween wires 16,16 of the upper screen (said portion corresponds to anarea indicated by a in the Figure). As a result, the jet stream passesthrough the lower screen under a resistance greater than that imposedthereon at the upper screen. However, the jet stream can pass throughsaid lower screen easily only with an increased resistance being imposedthereon. Accordingly, the passage of the jet stream through the assemblyscreen causes a crimping action in the screen depth. It is as if astuffing crimper of a small size were provided, Such crimper-like spaceis formed with respect to each perforation of the upper screen. Theassembly screen acts as if it were constructed with numerous smallcrimpers. Thus, the filaments undergo numerous folding crimping actions,and numerous folded crimps are formed in the filaments as shown bydotted lines in the Figure.

On the other hand, in accordance with the conventional process, theprinciple of which is illustrated in FIG. 4-B, such a multiple-crimperaction is not caused to occur, and only coarse crimps shown by dottedlines in the Figure are formed in the filaments.

In an embodiment shown in FIG. 5-A, the upper screen (indicated by solidlines: same in the following description) and the lower screen(indicated by broken lines: same in the following description) have thesame .dimensions and planar perforation configuration. The

two screens are overlapped in a manner such that each of wire crossingpoints of the lower screen is positioned almost at the center of theperforation of the upper screen. FIG. S-B illustrates an embodimentwhere a screen having a smaller mesh perforation than that of the upperscreen is used as a lower screen.

It is preferable to design a screen, particularly in the case of anassembly screen, in a manner such that the fluid which has'passedthrough the screen can escape therefrom freely without any hindrance.For instance, it is preferable to adopt a structure, the section ofwhich is illustrated in FIG. 6-A, in which the moving screen is composedof an assembly screen disk supported and fixed to a rotary shaft 1 l bymeans of a supporting member from which the jet stream which has passedthrough the screen'can freely escape. In the em bodiment shown in FIG.6-A, numerous small holes 9,9

. are perforated through a part of a frame 10 confronting the back of ascreen 7 hung on the frame and said part is supported and fixed to thehead of shaft 11, or a projecting part of the side wall of the frame 10may be supported and fixed to the head of the shaft 11 by means of aplurality of arms.

In the case of an endless belt type screen such as shown in FIG. l-B, itis important to avoid the vertical movement of the screen surface at theimpingement of the jet stream. This may be attained by impinging the jetstream against a roller 8, but this would not allow the stream to passthrough the screen. In such case, it is recommendable to adoptmodifications such as shown in FIGS. 6-H and 6-B, which have beenalready detailed in the above-mentioned prior application Ser. No.847,548. r

In short, it is recommendable to adopt a structure where the movingscreen is an endless belt of an assembly screen and an outlet forprojecting the heated jet stream is disposed at the position confrontinga groove provided on a rotary roll driving the assembly screen belt toallow the jet stream which has passed through the screen to freelyescape; or where the moving screen is an endless belt of an assemblyscreen and an outlet for projecting the heated jet stream is disposed atthe position confronting an arm space formed between two rotary disksdriving the assembly screen belt to allow the jet stream which haspassed through the screen to freely escape.

As is shown in FIG. 6-B, a circular groove is provided on a part of theroller 8 in the longitudinal direction thereof to thereby form a space 9and to arrange the jet 6 in a manner such that the jet stream from thejet 6 will impinge against the screen at a position confronting thegroove. Although the jet may be arranged in an optional positionconfronting the circular groove on the roller, it is preferred toarrange the jet 6 so as to confront a portion of the groove that isstill in contact with the assembly screen 7 but just before the portionat which the assembly screen 7 is released from the contact with theroller 8. No special restriction is given to said circular groove withrespect to configuration,

depth and the like. In short, any type of the groove is applicable asfar as it allows the jet stream to freely escape along the groove. Ifdesired, a roller comprising a circular die connected therewithconcentrically and having a diameter smaller than that of the roller maybe used. Further, it is possible to use two dies 8A,8A fixed to eachother by means of a plurality of arms (see FIG. 6-B' wherein thenumerical reference 12 represents an arm and the screen is not shown).It is sufficient that at least three arms are disposed. In case threearms are used, they are disposed in a manner such that each of the basesof the arms is a vertex of an equilateral triangle. Of course, it ispossible to dispose 4 or more arms in a polygonal pattern.

It is also recommendable in this invention to use as the feed roll forfeeding thermoplastic synthetic continuous filaments to the jeta roll inwhich the surface of the portion on the filament-introducing side has agreater coefficient of friction and the surface of the portion on theside forwarding the filaments from the roller for feeding them to thejet as a smaller coefficient of friction.

In the feed roll 3 shown in FIG. l-A, the dotted portion of the roll 3has a surface of a smaller coefficient of friction and the plain portionhas a surface of a greater coefficient of friction. In case such feedroll is used, since the portion of a smaller coefficient of friction isutilized for feeding filaments to the jet, the separation of thefilaments from the roll may be effected easily and smoothly. Thus, thefeeding of the filaments to the jet can be accomplished very smoothly.Further, since the filaments undergo a pre-shrinkage in this portion ofa smaller coefficient of friction, the shrinkage of the filaments in thejet can be controlled. At the same time, since the portion of a greatercoefficient of friction maintains the filaments stably, variations ofthe tension on the filaments can be prevented between the feed roll andjet. Accordingly, the use of such feed roll is effective to keep thefilament shrinkage constant during the operation.

In the crimping process to which this invention is directed, the feedingof filaments into a jet (or suction of filaments by a jet) dependsmainly on the fluid friction between the filaments and heated jetstream. In this case, the sucking tension is generally low. Forinstance, in the case of nylon of 210 d/34 fil, the total tension islower than about 4 g. Since the filament tension is so low as describedabove when the filaments pass through the jet, the shrinkage of thefilaments is naturally effected in the almost relaxed state. For thisreason, the shrinkage takes a form of a thermal shrinkage in whichvariations are likely caused to occur (though an extremely violentthermal condition being also one reason). Further, under such lowfilament tension the separation of filaments from the feed roll cannotbe accomplished smoothly. Therefore, a balance between the frictionalforce of the roll and filaments and the filament sucking force is easilyput into disorder, and variations are caused in the tension of thefilaments being introduced into the jet. Since the shrinkage of thefilaments in the jet is likely to be varied as mentioned above, suchvariations in the filament tension cause great influences on theshrinkage of the filaments in the jet, with the result that a deviationof the heat treatment effect is brought about and an undesirable dyeingunevenness is likely imparted to resulting crimped bulky filaments. Thisdisadvantageous variation of the tension of the filaments beingintroduced into the jet is multiplied by the shrinkage of the filamentsby the preheating.

The use of the above feed roll can exert the preheating effectsufficiently and prevent the above undesirable variation of the filamenttension and its multiplication by the pre-heating. On the other hand,the use of a feed roll, the entire surface of which exhibits the samecoefficient of friction, cannot exhibit any effect of preventing theabovementioned variation of the filament tension or its multiplication,though it may exhibit a pre-heating effect.

FIG. l-A illustrates an embodiment of the feed roll 3 where thecoefficient of surface friction of the portion on the filament-feedingside is different from that of the portion on the filament-forwardingside. Of course, it is possible to use a feed roll in which thecoefficient of surface friction is different among three or moreportions.

It is sufficient in such feed roll that a greater coefficient offriction is such as will not cause slips of filaments. With respect tothe number of turns of the filaments on such roll, we have found that itis sufficient to turn the filaments on the portion of a greatercoefficient of friction to such an extent as will not cause slips offilaments is dependent on the kind and monofilament denier of M thefilaments, the total denier of the filaments, the diameter of the feedroll and the like, it is difiicult to specify the range numerically. Butgenerally the coefficient of friction of the surface of thefilamentintroducing side is 0.3 to 0.4 and that of the surface of thefilament-forwarding side is 0.15 to 0.2. It is preferable that the ratioof the coefficient of friction of the surface on the filament-forwardingside to that of the surface on the filament-introducing side is lessthan 0.5. As a specific example of such feed roll there may be cited aroll which consists of a portion of a greater coefficient of frictionhaving a surface plated with hard chromium (a coefficient of friction of0.4) and a portion of a smaller coefficient of friction having a sandblasted metal (a coefficient of friction of 0.2).

It is general to dispose the end point of the jet nozzle at a positionapproximating considerably to the screen surface. The distance betweenthe end point of the jet nozzle and the screen surface is usually vernsmall and up to 10 mm, for instance, in an order of 1 mm to 7 mm, or 1.5mm to 5 mm. This distance becomes frequently almost equal to the heightof the deposit of the crimped filaments. This height is variantdepending on the processing conditions such as nozzle temperature,nozzle pressure, speed of the moving screen and feed rate (overfeedamount), and the denier of the fila-- ments, but it is generally about 1to 3 mm in the filaments of less than 500 denier and about 2 to 5 mm inthe filaments of 500 to 3,000 denier. Therefore, there is a danger thatfilaments fall in contact with the end point of the jet nozzle. In thecase of a jet having a naked end point of a processed metal such asshown in section in FIG. 7-A, when the distance between the nozzle endand the screen surface is made smaller, a chance of a contact of thefilaments with the outer wall of the jet is increased, and occurrence ofyarn breakages or fuzzings increases. Further, filaments which have onceadhered to the nozzle end melt to form fused dregs which are not easilyseparated from the nozzle end and, the presence of such dregs increasesthe chance of a contact of the filaments with the nozzle.

In order to attain an easy separation of such dregs from the vicinity ofthe nozzle hole, we have tried to apply to the outer wall of the jetnozzle a silicone oil type separating agent used in the customary meltspinning method for preventing solidification and agglomeration of dregsformed in the vicinity of spinning nozzles. However, the above trialcould not result in sufficient effects in the crimp processing processintended in this invention. On the contrary, since the formation of sucha thin film of a liquid on the outer wall of the nozzle shows a tendencyto heighten the thermal conduction of the filaments and quicken thefusion of the filaments adherent to the nozzle wall, the abovementionedtrial only promotes the occurrence of the abovementioned undesirablephenomenon.

In order to overcome such disadvantage, it is preferable in thisinvention that at least an end portion of the jet nozzle is composed of,or coated with, a material of a thermal conductivity of less than 3.0 Xcal/cm.sec.C. As such material there may be citedpolytetrafluoroethylene and ceramics which are resistant totemperatureshigher than 200C. and have a thermal conductivity of lessthan 3.0 X 10 cal/cm.sec.C.

FIGS. 7-B and 7-C illustrate the sections of nozzle ends, similar tothat shown in FIG. 7-A, which are composed of, or coated with, suchmaterial of a low thermal conductivity. In the Figures, the numericalreference 18 represents a metallic material constituting the nozzle, andthe numerical reference 19 represents a material of athermal-conductivity of lower than 3.0 X 10 cal/cm.sec.C.

As is illustrated in FIG. l-B, in this invention it is possible toprovide an additional jet 20 for projecting a heated jet stream to thefilaments on the moving screen while they are on the filament passagemoving according to the movement of the screen and within a distancewhere the filaments are maintained at a temperature above the glasstransition point thereof. The section of an example of the additionaljet 20 is shown in FIG. 8-A in which the reference 21 represents aninlet for a heated and compressed gaseous fluid, usually, heated andcompressed air, and the reference 22 represents an outlet for projectingsaid fluid. It is preferable that the configuration of the projectingoutlet 22, as is shown in FIG. 8-B, is of a rectangular form extendingin the direction (indicated by an arrow) of the filaments movingaccording to the movement of the screen.

As described hereinabove with respect to the improvement of the feedroll 3 for feeding filaments to the jet 6, the variations of theshrinkage of the filaments in the jet or on the screen caused by thevariations of the tension'of the filaments being introduced into the jetfrom the feeding roll result in the formation of dyeing unevenness ofthe resulting crimped bulky filaments. Accordingly, if the variations ofthe shrinkage are not caused to occur, the problem of the dyeingunevenness should naturally be solved at the same time. For attainingthis purpose it is recommendable to adopt means for projecting anadditional heated jet stream to the filaments deposited on the screenand having in this state variations of the shrinkage, while they aremaintained at a temperature above the glass transition point (secondtransition point) thereof, namely they are still in the fluid state.When such additional heated jet stream is projected to the filaments,the portion of a smaller shrinkage is further shrunk preferentially, andthe uneven shrinkage is corrected so that the shrinkage will besubstantially the same along the filament axis, with the consequencethat it is possible to obtain easily crimped bulky filaments exhibitinghardly any dyeing unevenness.

This invention will be now described by referring to examples.

The percentage crimp referred to examples is a value measured andcalculated in the following manner:

A sample of crimped filaments is dipped in boiling water for minutes inthe relaxed state to develop crimps. Then, the sample is taken fromwater and it is allowed to stand still for 24 hours so as to dry itnaturally. A load of 0.1 g/d is imposed on the sample and the lengththereof is measured (1 Then, the load is removed from the sample and aload of 2 mg/d is imposed on the sample and the length thereof ismeasured (1 The value of the percentage crimp is calculated from thefollowing formula:

Percentage crimp (1 1,), X 100 EXAMPLE 1 Runs of preparing crimped bulkyfilaments from filaments indicated in Table 1 below were carried outunder conditions indicated also in Table l. The results are shown inTable 1.

As is apparent from the results shown in Table I, an assembly screen oftwo screen layers exerts a greater force of retaining the filamentsthereon because of improved effects of leaving and depositing thefilaments by small spaces formed among screen wires, as compared with asingle screen. Therefore, in the case of the assembly screen, the effectattained by the pressing roll is conspicuous. Still further, as is alsoapparent from the results of Table l, the use of an assembly screenresults in crimped filaments excellent in crimp characteristics.

Notes 1. NDS is Nylon semidull.

2. TSD is Tetron semidull (Tradename of polyester filament produced byTEIJIN LIMITED).

3. NB is Nylon bright.

4. In each run using NSD filaments, the filament take-up rate was 520m/min. and the take-up tension was l5i2g.

S. In each run using TSD filaments, the filament takeup rate was 820m/min. and the take-up tension was 7 i 2 g.

6. In each run using NB filaments, the filament takeup rate was 320m/min. and the take-up tensionwas i 10 g.

'7. As the screen of the disk type there shown in FIG. l-A.

8. As the screen of the endless belt type there was used that shown inFIG. l-B.

9. The value given in parentheses in column screen mesh is the value ofthe perforation ratio of the screen used.

was used that EXAMPLE 2 In this example there was used the apparatusshown in FIG. l-B Nylon-6 continuous filaments of 2 d] 1 36 fil wereheated by a feed roll maintained at C. and fed at a rate of 500 m/min.into a jet nozzle maintained at a temperature of 230C. at a compressedair pressure of 5 Kg/cm (gauge). The filaments were projected from thenozzle together with the heated and compressed air and impingedcontinuously against an endless belt of a metal wire of 10 X 15 meshmoving at a rate of 50 m/min. On the moving belt they were cooled andwound up at a rate of 400 m/min. while adjusting the take-up tension to0.03 g/d when they were separated from the pressing roll. In this run,the point of separating the filaments was fixed at the point pressed bythe pressing roll and the operation could be carried out very stably.

When the resulting filaments were subjected to the tufting operation asthey were prepared without being twisted, the tufting could be effectedsmoothly without entanglements of filaments with guides or needles. Themechanical efficiency of the tufting operation was 80 85 percent. Themechanical efficiency of the tufting is a measure for evaluating theeasiness of the tufting operation and expressed in the terms of theratio of the time during which the tufting machine is actually operatedto the total of said time and the time during which the tufting machineis stopped. in the usual tufting operation, mechanical efficiency of thetufting is in the range of about 70 to about 90 percent.

EXAMPLE 3 In this example there was used the apparatus shown in FIG.l-B. Polyethylene terephthalate filaments of 75 d/36 fil were fed at arate of 1,000 m/min. by means of a feed roll maintained at 170C. whichacted also as a preheating roll and passed through a nozzle containing aheated compressed air of 260C. and 5 Kg/cm (gauge) having an action as alaminar flow. Then, they were impinged together with the heatedcompressed air against an assembly screen of 40 X 40 mesh and crimpedthereon. Then, they were cooled and wound up to obtain crimped bulkyfilaments.

The above run was repeated in the same manner as above except that anadditional jet was provided 5 cm after the above cimping nozzle forprojecting a heated compressed jet stream, and an additional heatedcompressed air of 270C. and 3 Kg/cm (gauge) was projected therefrom. Asa result there were obtained crimped bulky filaments having a percentagecrimp of 25 percent and a dyeing uneveness evaluation of 4.5.

In the above runs, because the pressing roll 1 was used, the operationwas effected very smoothly. But, if the runs were conducted withoutusing the pressing roll 1, the variations of the take-up point wereextreme and the continuous operation was impossible.

The evaluation of the dyeing unevenness was based on 5 grades. In casethe dyeing unevenness is permissible in the practical use, the dyeingunevenness evaluation was determined to 3. In case the dyeing unevennesswas too great, the evaluation was determined to be 1, while in case thedyeing unevenness was scarcely or not observed, the evaluation wasdetermined to be 5.

EXAMPLE 4 In this example there was used the apparatus shown in FIG.l-A. Polyamide filaments of 210 d/34 fil were fed at a rate of 700m/min. by means of a feed roller maintained at 130C. which acted also asa preheating roll and passed through a nozzle of a heated compressed airof 250C. and 5 Kg/cm (gauge) having an action as a laminar flow. Then,they were impinged against an assembly screen consisting two layers ofscreens of 30 40 mesh, and crimped thereon. They were then cooled andwound up to give crimped filaments.

As the pre-heating roll there was used a roller consisting of afilament-introducing portion having a chromium-plated surface of acoefficient of friction of 0.4 and a filament-forwarding portion havingan aventurine surface of a coefiicient of friction of 0.2. Results areshown below.

Percent Thermal shrinkage Thermal Evaluation during Shrinkage shrinkageof dyeing Pre-heatlng roll operation by nozzle on roll Criiupsunevenness Chromium plated surface (3 turns) Aventurine surface (9turns) 13 S 30 5 In the above run, the use of the pressing roll 1 madeThe chrimp-processing operation was carried outby it .possible to effectthe operation very stably, while when the above run was repeated withoutusing the pressing roll 1, the point of separating the filaments fromthe screen was greatly varied and the continuous operation wasimpossible. Thus, it is understood that this invention has made itpossible for the first time to succeed in the actual'preparation ofcrimped filaments by utilizing hot air, which the prior art fails topractice in an industrial scale.

EXAMPLE 5 In this example there was used the apparatus shown in FIG.l-A. Polyethylene terephthalate continuous filaments of 75 d/36-fil werefed at a rate of 1,000 m/min. by a feed roll maintained at 170C. to anozzle maintained at 260C. and a compressed air pressure of 5 .Kg/cm(gauge). They were continuously projected together with the compressedair on a disk wire screen rotating at a peripheral speed of 60 m/min. toform crimped filaments. In this example, the nozzle having an endportion such as shown in FIG. 7-B was used, wherein apolytetrafluoroethylene resin of a thermal conductivity of 0.01 X -l0.''cal/cm.sec.C. was coated on the nozzle .zproper composed of brass of athermal temperature at 260C. As a result there were obtained crimpedbulky filaments having very excellent properties.

The use of the pressing roll 1 in these runs made it possible to conductthe'continuous operation very stably ata high producibility, while whenthe pressing roll 1 was not used, the variation of the yarn-take-uppoint was extreme and the continuous operation was impossible.

EXAMPLE 6.

In this example was used a nozzle such as shown in FIG. 3-A, in whichthe projecting opening diameter was 1.8 mm, the projection nozzle lengthwas 30 mm, the inner diameter of the guide needle was 1.0 mm and theouter diameter thereof was 1.4 mm. When the operation was effected at anozzle temperature of 250C. and a compressed air pressure of 5 Kg/cmwhile passing polyamide filaments of 210 d/34 fil through the nozzle, itwas found that a good balance was established between the sucking forceand the force of the backward flow when the extending length AL of theguide needle was 1.2 mm. Thus, a desirable weak backward flow wasattained. lt was confirmed by a stroboscopic photograph that thefilaments were projected linearly.

maintaining the nozzle at the above-mentioned state" and impingingpolyamide filaments indispensable 210 d/34 fil fed at of 700 m/ min. andpre-heated at the nozzle maintained at 250C., onto a rotating,airpermeable assembly screen consisting of two screen layers of 30 meshand 40 mesh. As a result, there were obtained crimped bulky filaments ofa percentage crimp of 30 percent, while the operation was conducted verystably.

It was found that even under such conditions as above where thefilaments were projected linearly, it was indispensable to use thepressing roll 1 such as shown in FIG. l-A in order to conduct thecontinuous operation in the stable condition, and that when theoperation was conducted without using such pressing roll, theyam-take-uppoint shifted extremely and the continuous operation wasimpossible.

We claim: W

1. In apparatus for preparing crimped bulky filaments including a feedroll for feeding thermoplastic synthetic continuous filaments to anozzle for projecting a heated jet stream accompanying the filaments fedto said nozzle, a moving screen upon which the heated jet streamimpinges and which allows the heated jet stream to pass through whileleaving the filaments of said screen, and a take-up roll for separatingthe crimped filaments from said screen at a separation point, thecrimped filaments having been cooled according to movement of the screenbetween the impingement point and the separation point, the improvementcomprising means holding the filaments on said screen at the separationpoint to prevent movement of the separation point.

2. The apparatus described in claim 1 wherein said nozzle includes ahousing having a chamber defined therein to receive a heated andcompressed gaseous fluid and a tubular passage communicating with saidchamber for projecting the fluid; and a hollow guide needle forreceiving the filaments, said guide needle being disposed coaxially withsaid passage to penetrate said housing, said guide needle extendingthrough said chamber and extending into said passage a distance lessthan one-half of the entire length of said passage to form an annularpassage for the fluid between said needle and the inner wall of saidpassage.

3. The apparatus described in claim 1 wherein said means for preventingmovement of the separation point includes a conical pressing rollcontacting said screen at the separation point.

4. The apparatus described in claim 1 wherein said moving screen is anassembly screen including at least a perforated upper screen and aperforated lower screen, the plane perforation area of each portion ofsaid lower screen overlapping each perforation of said upper screenbeing smaller than the plane area of each perforation of said upperscreen, said portion of said lower screen having an open spacesufficient for the jet stream to pass through said portion and freelyescape from the assembly screen.

5. The apparatus described in claim 4 wherein said upper and lowerscreens are spaced by a distance of up to 2mm. and said assembly screenhas a perforation ratio of from to 70 percent.

6. The apparatus described in claim 1 wherein said feed roll for feedingthe thermoplastic synthetic continuous filaments is a roller having afirst portion receiving the filaments and a second portion feeding thefilaments to said jet, said first portion having a surface with acoefficient of friction of at least 0.3 and said second portion having asurface with a coefficient of friction of less than 0.2.

7. The apparatus described in claim 6 wherein said first portion has asurface with a coefficient of friction in the range of 0.3 to 0.4 andsaid second portion has a surface with a coefficient of friction in therange of 0.15 to 0.2, and the ratio of the latter coefficient to theformer coefficient is less than 0.5.

8. The apparatus described in claim 1 wherein said nozzle has an endportion composed of, or coated with. a material having a thermalconductivity of less than 3.0 X 10 cal/cm. sec. C.

9. The apparatus described in claim 8 wherein said material is selectedfrom the group consisting of polytetrafluoroethylene resins andceramics.

10. The apparatus described in claim 1 and further comprising anadditional nozzle projecting a heated jet stream on the filaments onsaid moving screen at a position where the filaments are maintained at atemperature above the glass transition temperature of a polymerconstituting the filaments.

11. The apparatus described in claim 1 wherein said means for preventingmovement of the separation point includes a cylindrical pressing rollcontacting said screen at the separation point.

12. The apparatus described in claim 1 wherein said means for preventingmovement of the separation point includes suction means disposed on aside of said screen opposite the take-up roll.

1. In apparatus for preparing crimped bulky filaments including a feedroll for feeding thermoplastic synthetic continuous filaments to anozzle for projecting a heated jet stream accompanying the filaments fedto said nozzle, a moving screen upon which the heated jet streamimpinges and which allows the heated jet stream to pass through whileleaving the filaments of said screen, and a take-up roll for separatingthe crimped filaments from said screen at a separation point, thecrimped filaments having been cooled according to movement of the screenbetween the impingement point and the separation point, the improvementcomprising means holding the filaments on said screen at the separationpoint to prevent movement of the separation point.
 2. The apparatusdescribed in claim 1 wherein said nozzle includes a housing having achamber defined therein to receive a heated and compressed gaseous fluidand a tubular passage communicating with said chamber for projecting thefluid; and a hollow guide needle for receiving the filaments, said guideneedle being disposed coaxially with said passage to penetrate saidhousing, said guide needle extending through said chamber and extendinginto said passage a distance less than one-half of the entire length ofsaid passage to form an annular passage for the fluid between saidneedle and the inner wall of said passage.
 3. The apparatus described inclaim 1 wherein said means for preventing movement of the separationpoint includes a conical pressing roll contacting said screen at theseparation point.
 4. The apparatus described in claim 1 wherein saidmoving screen is an assembly screen including at least a perforatedupper screen and a perforated lower screen, the plane perforation areaof each portion of said lower screen overlapping each perforation ofsaid upper screen being smaller than the plane area of each perforationof said upper screen, said portion of said lower screen having an openspace sufficient for the jet stream to pass through said portion andfreely escape from the assembly screen.
 5. The apparatus described inclaim 4 wherein said upper and lower screens are sPaced by a distance ofup to 2mm. and said assembly screen has a perforation ratio of from 20to 70 percent.
 6. The apparatus described in claim 1 wherein said feedroll for feeding the thermoplastic synthetic continuous filaments is aroller having a first portion receiving the filaments and a secondportion feeding the filaments to said jet, said first portion having asurface with a coefficient of friction of at least 0.3 and said secondportion having a surface with a coefficient of friction of less than0.2.
 7. The apparatus described in claim 6 wherein said first portionhas a surface with a coefficient of friction in the range of 0.3 to 0.4and said second portion has a surface with a coefficient of friction inthe range of 0.15 to 0.2, and the ratio of the latter coefficient to theformer coefficient is less than 0.5.
 8. The apparatus described in claim1 wherein said nozzle has an end portion composed of, or coated with, amaterial having a thermal conductivity of less than 3.0 X 10 2 cal/cm.sec. * C.
 9. The apparatus described in claim 8 wherein said material isselected from the group consisting of polytetrafluoroethylene resins andceramics.
 10. The apparatus described in claim 1 and further comprisingan additional nozzle projecting a heated jet stream on the filaments onsaid moving screen at a position where the filaments are maintained at atemperature above the glass transition temperature of a polymerconstituting the filaments.
 11. The apparatus described in claim 1wherein said means for preventing movement of the separation pointincludes a cylindrical pressing roll contacting said screen at theseparation point.
 12. The apparatus described in claim 1 wherein saidmeans for preventing movement of the separation point includes suctionmeans disposed on a side of said screen opposite the take-up roll.